Phased array antenna

ABSTRACT

A phased-array radar antenna system has a scan pattern which is pivotal about the center of the array. The scan pattern is directed from a common set of scan-control circuitry which consists primarily of digital counters and logic whose output describe the settings of ON-OFF ferrite phase shifters for the elements on one side of the array. The one&#39;&#39;s complements of these outputs are used to control the settings for the other one-half of the array, without need for an extra least bit. Each phase shifter consists of four bits. When all four bits are in their ON state, a phase shift of 360* is obtained. The minimum or increment of phase shift is 24*.

[ 51 July 17,1973

1 1 PHASED-ARRAY ANTENNA [75] inventors: George M. Kirkpatrick; NormanR. Wild, both of North Syracuse, N.Y.

[73] Assignee: Syracuse University Research Corporation, Syracuse, NY.

[22] Filed: July 23, 1970 [21] Appl. No.: 57,618

[56] References Cited UNITED STATES PATENTS 4/1968 Connolly 343/100 SAUX 12/1966 Hair 333/24.1

Primary Examiner-Samuel Feinberg Assistant Examiner-Richard E. BergerAttorney-Paul & Paul [57] ABSTRACT A phased-array radar antenna systemhas a scan pattern which is pivotal about the center of the array. Thescan pattern is directed from a common set of scancontrol circuitrywhich consists primarily of digital counters and logic whose outputdescribe the settings of ON-OFF ferrite phase shifters for the elementson one side of the array. The one's complements of these outputs areused to control the settings for the other one-half of the array,without need for an extra least bit. Each phase shifter consists of fourhits. When all four bits are in their ON state, a phase shift of 360' isobtained. The minimum or increment of phase shift is 24.

18 Claims, 8 Drawing Figures SCAN GENERATOR PULSE RECEIVER PATENIEUJUL 11 m5 SHEET 1 [1F 5 if a mokdmmzww 240w kw mm QOPDQEkmE mm ba ATTORNEYS,

PATENIED JUL 1 7 SHEEI 2 0F 5 MICROWAVE FERRITE PHASESH\FTERS 'x DIPOLEFROM TRANSMITTER TO RECEWER C i I E LATCHING WlRES--- i .L SCR ORTRANSISTOR\ DRIVERS THE LOGIC SELECTS ONES SW'TCHES I COMPLEMENT FORRECEIVE (LOGC) A x A i CONTROL PULSES i Q i 0 10 1O 1 CLOCK PULSES FF FFFF FF -dc COUNT UP i i U COUNT DOWN PHASESHIFTERS 5) FROM CORPORATE FEED[f] DRIVERS Q aNARY COUNTERS (FE) r PULSE INPUTS l NPOT PULSES PERSECOND N N N Fig. 3

INVENTORS George M. Kirkpotnck By Norman R. Wild ATTORN EYS.

PATENIED 1 3. 747. 098

saw u or 5 INVENTORS.

ATTORNEYS.

TIMING PULSES TRANSMlT/RECEIVE CLOCK PULSES George MKirkpcIrick Norman RWild BIT1 DRIVER BIT 1 BIT 2 DRIVER SIT 2 I COUNTER OII I BIT 4 DRIVERGATES GATES GATES BIT 4 BIT 8 DRIVER GATES z wEw TO/ FROM TRANSMITTER/DUAL CLR DRIVER RECEIVER RESET OR CLEAR PAIENIED 1 3. 747. 098

sum 5 0r 5 lNPUT INPUT 2N5|83 FERRITE 2N5|83 BT lOK; l l IOK DUAL RESETDRIVERS Fig 8 INVENTORS. George M. Kirkpatrick BY Norman R. Wild WY MEATTOR N EYS PHASED-ARRAY ANTENNA FIELD OF THE INVENTION The presentinvention relates to scanning antennas for radar, and in particular tophased-array radar antennas.

ln phased-array radar antennas of the type here involved, the radiatingelements are arranged in a rectangular array of rows and columns, andthe transmit signals applied to each column of radiating elements arephase-shifted relative to the transmit signals applied to the othercolumns of elements, thereby to shape and position the beam in space. Bychanging the phase shifts for succeeding pulses, the beam is steeredback and forth. The scanning rates may, of course, be substantiallyhigher than where the beam is steered by a mechanically rotating dish.

While phased-array or electronic scanning radar antennas may be used inground installations, they are particularly suitable for airborne orspaceborne application since their construction is substantially lighterin weight than that of mechanical rotating dish antennas. A phased-arrayantenna may, for example, be fitted into the nose or wing of an aircraftwithout disturbing the aerodynamic lines of the craft.

The phased array of radiating elements may be fed through either seriesor corporate feed. Each branch may include a phase-shifter which isdigitally controlled electronically. The phase shifters may bereciprocal or non-reciprocal in their action.

OBJECTS OF THE INVENTION A principal object of the present invention isto provide a phased-array radar antenna the radiating or dipole elementsof which are under the control of ON- OFF ferrite phase shifters whichare non-reciprocal in their action, and in which each phase shiftercomprises a plurality of individually controlled ferrite units, whichwill be referred to herein as bits."

Another object of the invention is to provide a phased-array radarantenna system having a scan pattern which is pivotal about the centerof the array, and in which the scan pattern is directed from a commonset of scan control circuitry, consisting primarily of digital countersand logic, whose outputs describe the phase-shifter settings for theelements on one side of the array, and the ones complements of theseoutputs describe the settings for the other side of the array.

Another object of this invention is to provide an improved method, orimproved circuitry, for utilizing current pulse driver circuits tocontrol the 4-bit binary phase shifters of the antenna system.

While the invention is applicable to systems employing phase shifters ofother than four bits, it will be convenient to describe a system inwhich four-bit binary phase shifters are used. These four bits areweighted in the ratios of l, 2, 4 and 8.

BACKGROUND OF THE INVENTION In a linear phased-array radar antennasystem, the beam is steered by controlling the relative phase of themicrowave energy emitted from the radiating elements in a linear manner.The phasing of the energy delivered to each radiating element must beproportional to the distance of the element from the point on the arrayabout which it is desired to pivot the beam. If the elements are spacedequidistant, then the microwave energy to the first element from thepivot point will be shifted by an amount of q), the energy to the secondelement will be shifted by an amount of 2gb, the energy to the thirdelement will be shifted by an amount of 3d), and so on.

Since phase shifts beyond 360 are redundant, it would seem appropriate,in the development of a 4-bit phase shift system, to design the systemon the basis of an incremental unit of phase shift of 360/2, or 22%".Stated in somewhat more technical terms, it would seem that theincremental or minimum unit of phase shift Atb would be (211 radians)/2"where n is the number of bits. Thus, for a 4-bit phase shifter, thesmallest unit of phase shift Ad) would be 21r/2== 21r/l6=1r/8 radians,or 22- /2". Hence, the smallest ON-OFF phaseshifter bit would have aphase increment of either zero when OFF or 22-;6 when ON. Each of theother phaseshifter bits would have values ofeither zero, when OFF, ortwice that of one of the other phase-shifter bits, when ON. Accordingly,the bits of the 4-bit phase shifter would, on this basis, accomplishphase shifts of zero, when OFF, or of 22-%, or 45, or or 180", when ON.It will be understood that, on this basis, the phase shift introduced byeach of the latching ferrite bits is zero, when the ferrite bit is inone of its two states, denominated OFF, and would be 22-56, or 45, or90, or 180, when the ferrite bit is in its other state, denominated ONIt was indicated above that a principal object of the present inventionis to provide a phased-array radar antenna system having a scan patternwhich pivots about the center of the array and in which the scan-controlcircuitry uses complements to control one-half of the array. In usingcomplement control, a single control wire controls two phase-shifterbits, one on each side of the array. A pulse signal on this wire setsone ferrite bit on one side of the array to a particular state (1 or 0)and sets the corresponding ferrite bit on the other side of the array tothe complement (0 or 1 Unfortunately, the complement obtained in thismanner is the ones" complement, also known as the diminished radixcomplement, rather than the required "twos" complement. The twos"complement, or radix complement, differs from the ones" complement byone bit of the least significant bit. Consider the following binarynumber 0110. The ones" complement (the bits inverted) is 1001, but thedesired twos" complement is 1010, which is one bit larger.

There are several ways of adding the extra bit. One way would be bybinary adders. Another way would be by addition ofa least bit phaseshift to each antenna element on the side of the array using thecomplement. Thus, a 1r/8 phase shifter would be used in addition to theregular 4-bit phase shifter.

The other use for the complement is in switching the array from transmitto receive. As indicated previously, the present invention relates tonon-reciprocal phaseshifter action. With non-reciprocal phase shifters,the array must be switched to the receive position immediately followingthe transmit pulse. This may be done by using the complements to switchthe array. In such case, the ones" complement is correct, as each phaseshifter must be magnetized in the opposite direction to the transmitcondition. The extra bit added to each element receiving the complementprior to transmit must also be reversed. If the beam is initiallyscanned to the right of the normal, then the left hand set of phaseshifters receives the binary number, and the right hand side receivesthe complement plus one bit. This is equivalent to providing negativephase shifts to the right side. When the beam is scanned to the left ofthe normal, then the right side uses the binary count, and the left sidereceives the complement plus one bit. Therefore, the extra bit must beon the right side when the beam is on the right, and must be on the leftside when the beam is on the left.

It will be understood from the foregoing that where the least bit sizeis determined by the relation A=21r/2", and an extra bit is needed, andis added, each binary phase shifter would have five bits, two of whichwould be least bits. Moreover, an extra driver would be required on eachside of the array to insert or remove all eight of the least bits inunison.

SUMMARY OF THE INVENTION As indicated previously, one of the objects ofthe present invention is to provide a scan-control system for aphased-array radar antenna which avoids the need for the extra bit.

The above object, as well as the other previously recited objects of theinvention, are accomplished by providing a scan-control system in whichthe binary phase shifters use a least bit size determined by theequation A=21r/(2"l rather than by the equation A=21rl2", as heretoforediscussed. Thus, the present invention proposes that the least bit ofthe binary phase shifters be of such size so that the sum of the bits ofthe phase shifters totals 211 radians or 360, rather than 360 minus22%;.

Restated, the present invention provides a scancontrol system for aphased-array radar antenna in which the binary phase shifters have aminimum bit size determined by the following equation: A=21r(2"l Thus,for a 4-bit phase shifter, where n=4, the least bit size equals 360/(l6-l )=24.

The following is a truth table for n=4 and a bit size given by theequation A=360/(2"-1 TABLE 1 Table For Bit Size A=21rl(2"1) for n=4Series Input Phase Shifter Control Signals Total Phase Shift pulse1611/15 81r/l5 41r/l5 21r/l 5 radians degrees No.

1] l) l) 0 0 1| 1 l 1 1 21: 360 l 0 0 0 1 211/15 24 1' l l l O 281r/l336 2 0 0 l 0 411/15 43 2 l l 0 1 261r/l5 312 3 0 0 l l 61r/l5 72 3' l lO 0 241r/l5 288 4 0 l 0 0 Err/l5 96 4 l 0 l l 221r/l5 264 5 0 1 0 lIO'rr/IS 120 5 l O l 0 201/15 240 6 0 l 1 0 121:!15 144 6' l 0 0 1I81r/l5 216 7 0 l l l l41r/15 I68 7' l 0 0 0 l61r/l5 192 B l 0 0 0161r/l5 192 8' O l l l l4'll5 168 9 l 0 0 l l81rll5 216 9' 0 l 1 0IZ'Ir/IS 144 10 l 0 l 0 2011415 240 1D 0 l 0 l 101r/15 120 l l 1 0 l I221lll5 264 1 l 0 l 0 0 81r/1S 96 12 1 l 0 0 2411-115 288 I2 0 0 l 161/15 72 13 1 l 0 1 261r/15 312 l3 0 0 I 0 41r/1S 48 14 l l l 0 ZlIw/lfi33b 14' (I 0 (I l 21r/l 5 24 l5 1 l I l 211 M10 l5 0 (I 0 (I 0 0 l6 0 ll0 0 ll 0 lo I l l I In 360 The prime indicates ones complementsInspection of the foregoing table for 4-bit phase shifters with bit sizein accordance with the equation Ad =21r/(2 1 where n=4, shows thefollowing:

a. the "ones" complement is satisfactory since the sum of the phaseshift plus the complementary phase shift for each number is 360.

b. the phase shift totals 360 (or 0) on both of counts 15 and 16.Therefore, there is a redundant setting, and count 15 must be avoided.This may be done by adding an extra count when 15 is reached. This maybe done by the use of a counter for each dipole element on one side ofthe array.

The method proposed by the present invention of determining the leastbit size of the phase shifters by the relation A=21r/(2"l) has theadditional advantage, previously indicated, of decreasing the number ofdrivers which would otherwise be required.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagramillustrating a corporate feed to a l7-dipole array and the scan controltherefor;

FIG. 2 is a block diagram illustrating the control system for the 4-bitferrite phase-shifter of one of the dipole elements;

FIG. 3 is a block diagram illustrating the pulse inputs to the binarycounters;

FIG. 4 illustrates, on a greatly enlarged scale, the meander line of aphase shifter;

FIG. 5 is an elevational view, in section, of a ferrite phase-shiftershowing the ferrite torid through the center hole of which the meanderline passes;

FIG. 6 is a perspective view of a 4-bit ferrite phaseshifter showing thefour ferrite torid.

FIG. '7 is a schematic diagram of the presently preferred driver system;

FIG. 8 is a schematic of the reset drivers.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a simplified blockdiagram showing the corporate feed to an illustrative radar array whichis seventeen dipole elements wide and eight dipole elements high. Eachphase shifter FS feeds eight verticallyarrayed dipole elements. Theseventeen-dipole wide array is symmetrical on each side of a centerelement BC, the elements being identified as E1 to E8 on one side ofcenter and E1 to E8 on the other side. A hybrid arrangement is used todistribute energy equally to the eight vertically-arrayed dipoles fed byeach phase shifter.

It will be assumed that the antenna is operated at 10 ghz (gigahertz),which is 10 billion cycles per second. A wavelength at this frequency is0.8 inches (approx.) and accordingly each dipole element is about 0.4inch long. The entire dipole array occupies a rectangular area about 12inches wide and 6 inches high.

In FIG. 1, a transmitter T is shown for applying the microwave radarpulse signal R to the seventeen-dipole wide array through to atransmit-receiver TR box. Following the transmit period, a period of 5to 10 microseconds ma be allowed for switching the array from transmitto receive or listening condition. The listening period may, forexample, be 950 microseconds in duration. Following the receive orlistening period, 50 microseconds may be allowed for switching to thetransmit condition and for placing the beam in a new position. Duringthe 50 microseconds which are allowed for switching from receive totransmit, the scan generator SO delivers the necessary pulse scansignals S to place the 4-bit ferrite phase-shifters F8 in the ON-OFFstates necessary to determine the new beam position.

In FIG. I, in order to simplify the drawing, the rectangles identifiedFS represent not only the 4-bit ferrite phase-shifters FS but also theircontrol components, including counters, logic switches, current drivers,etc. Further details of these control components are schematically shownin FIGS. 2, 7 and 8.

Referring again to FIG. 1, the array illustrated contains seventeenequidistantly spaced elements, and it is desired to pivot the beam aboutthe center element of the array. Thus, there is a center radiatingelement BC with eight elements symmetrically located on each side ofcenter. Associated with each of the radiating elements, there is a fourbit phase shifter to control the phasing of the energy delivered to theelement.

Since the array is constructed to be symmetrical about its center, tosteer the beam the phasing of the microwave energy required by anelement on one side of the array must be of the same degree but oppositein sign as that required of the corresponding element on the other side.For example, in FIG. 1, where the elements are numbered E1 through E8 onthe one side of center, El thru E8 on the other side, and EC for thecenter, and it is determined that to steer the beam to a particularangle, the microwave energy of E6 requires to be shifted in phase by anamount if), then the energy of E6 must be phase shifted by an amountSince phase is a relative measurement, negative phase shifts arerealized by taking 360 Similarly, phase shifts of greater than 360 areredundant, and it is only necessary for the phase shifters to cover therange of 0 to 360.

As shown in FIGS. 2, 3, 6 and 7, each phase shifter is constructed offour ferrite cores or bits, with the bits weighted in the relativeratios of 8, 4, 2 and l. The ferrite bits are two-state devices whichare switched from state to state by current pulse driver circuitsdirected from the scan control circuitry. One state of the ferrite bitsis designated as an OFF state, and is taken as the reference state. Ifthe bit is switched to its 0N state, additional phase shift over andabove that due to the reference state is realized. When all four bits ofthe phase shifter are in their ON states, 360 of phase shift areobtained. Theoretically, the four-bit phase shifter could be used todivide the 360" into increments of 22 However, we have discovered thatdue to the nature of the phase shifter and the linear phased arrayantenna system, there are advantages to using the slightly largerincrement of phase shift of 24. Accordingly, this is the increment ofphase shift used in the phase shifters of the present application.

If the phase shifter setting is represented by a binary number ABCD,where A is associated with the 8-bit B with the 4-bit, C with the 2-bit,and D with the 1 bit, and where A, B, C, and D have a binary notation ofl or 0, corresponding respectively to the ON and OFF states of the bits,then the following Table 2, defines the possible phase shift settingsobtainable from the four bit phase shifters.

TABLE 2 Degrees Phase Shift I68 I92 216 240 264 288 3l2 336 360 A firstadvantage of the 24 phase shift increment is that the negative phaseshifts, realized by taking 360" are readily obtainable from the scancontrol circuitry. As can be seen from Table 2, for any of the possiblephase shift settings 360 is the one's complement of it. The onescomplement of a binary number is obtained by simply changing l s to 0'sand 0's to 1'5. For example, from Table 2, the phase shift setting for96 is (M00). The negative phase shift of 96 would be the ones complement(10H which represents a phase shift of 264 and which is 360 96".

In digital circuitry of the scan control, where the pri mary controlelement is the flip-flop circuit, the normal one and the inverted zerooutputs are both directly available, and thus, for any phase shiftsetting number, the one's complement number for the correspondingnegative phase shift is also available.

Another use of the ones complement of the phase shift setting, is inswitching the array from a transmit to a receive condition. The phaseshifter is a nonreciprocal device. The phase shift necessary for themicrowave energy when it is being delivered to the radiating dipoleelements in the transmit condition is different from that of the receivecondition, when received energy is being collected from the elements.The phase shifter setting for receive must be the ones complement of thetransmit setting, as each phase shifter ferrite bit must be switched tothe opposite state of its transmit condition. Therefore, just prior totransmit pulse time in each radar pulse repetition period, a transmitbeam steering angle is entered into the phase shifters. Then, justfollowing the transmit pulse time, the one's complement of each of thephase shifter settings is entered for the receive beam steering angle.

To generate the phase shifter settings for each of the beam steeringangles of the antenna scan, the scan control circuitry uses eight 4-bitdigital counters. Each of the counters is associated with a pair ofphase shifters, located in corresponding positions on opposite sides ofthe array. This is illustrated in FIG. 7. The phase shifter associatedwith the center element of the array requires no counter, as its phaseshift setting is kept constant at 0 relative phase shift for all beamsteering angles. The antenna scan produced is unidirectional, startingat ap proximately 45 left of the normal to the array center, andscanning to approximately 45 to the right of the normal to the arraycenter.

The 4-bit digital counters are constructed of flipflops, with both thenormal one and inverted zero outputs provided. The counter outputs arepro-vided to gating circuits, where the appropriate outputs areselected, depending upon whether it is a transmit or receive phaseshifter setting. The outputs of the gating circuits trigger the currentpulse driver circuits which switch the phase shifter ferrite bits to theproper states.

A second advantage of the 24 phase shifter increment is that it allowsthe number of current pulse driver circuits required by the phaseshifters to be minimized. As stated previously, the phase shiftersetting of an element on one side of the array is always the onescomplemcnt of the setting of the corresponding element on the other sideof the array. This is the case, whether it is a transmit or a receivesetting.

The current pulse required to switch the ferrite bits of the phaseshifters must be relatively large in magnitude, in the order of amperes.Since many ferrite bits are required to be switched simultaneously, alarge peak demand during the switching time would be placed on thesystems power supply, if the driver circuits were allowed to draw thenecessary current directly from the supply.

In accordance with a feature of the present invention, and asillustrated in FIG. 8, each driver circuit is provided with a storagecapacitor to store the energy to provide a sufficient current pulse atthe switching time. During the radar pulse period, the capacitor isallowed to re-charge for the next switching time. In this manner, thedemand peak on the power supply is decreased, but because of therecharge time of the drivercircuit storage capacitors, a driver circuitis not able to be used to set in both transmit and receive phase shiftsettings. However, because of the manner the driver circuits areimplemented in this invention, this restriction is of no consequence. Itis never necessary to use the same set driver circuit for both transmitand receive settings in the same radar pulse period. The number ofdriver circuits are also minimized, as shown in FIG. 7, in that onedriver circuit is used to set corresponding bits in corresponding phaseshifters on each side of the array. For example, bit 4 of E6 and bit 4of E6 are both set by the same driver circuit. A total of 32 set driversare thus required for elements El thru E8 and EI' thru E8. The methodfor entering phase-shift settings into a pair of corresponding phaseshifters one on each side of the array, is described as follows:

Step I: Just prior to transmit time, all bits of the phase shifter onthe left side of the array are cleared to the one state and those on theright side are cleared to the zero state. This operation is performed bythe clearing current pulse drive circuits CLR in FIG. 7.

Step 2: The transmit phase shifter settings are entered in by the setcurrent pulse drivers. The direction of the current pulse in its coursethrough the ferrite cores of the phase shifter will cause the bit stateson the left side of the array to be switched from one to zero and thoseon the right side from zero to one.

Step 3: The radar then transmits its microwave energy.

Step 4: The phase shifter bits on the left side of the array, are againcleared to the one state and on the right side to the zero state by theclearing current pulse driver CLR.

Step 5: The receive phase shifter settings are entered by the setcurrent pulse drivers. The settings remain until the next radar pulseperiod.

An example of the above sequence of events is as follows:

Step LEFT RIGHT B 4 2 l 8 4 2 l l l l l 1 0 0 0 0 2 l 0 l I 0 l 0 0 3TRANSMIT 4 1 l l 0 0 0 0 5 0 l 0 0 l o l I It can be seen that the setcurrent pulse driver for bit 4 is only used during step 2 and the setcurrent pulse drivers for hits I, 2, and 8 are used only in step 5.Thus, any one set current pulse driver is used only once per radar pulserepetition period.

Since the reset drivers must be operated twice during eachtransmit-receive cycle, the reset drivers are dual, as shown in FIG. 8.That is, two reset drivers are connected to each reset wire, since thestorage capacitors, C1 or C2, will not be able to recharge in thelimited time (less than microseconds) between the two reset operations.

A preferred construction of the 4-bit ferrite phase shifters isillustrated in FIGS. 4, 5 and 6 of the drawing. Each of the 4-bitferrite phase shifters consists of three basic configurations asfollows: (a) the basic meander line ML on Tellite board Te as shown inFIG. 4; (b) the ferrite toroids FT and tellite Te between the groundplanes GP, as seen in elevation in FIG. 5; and (c) the ferrite toroidsFT, insulating spacers I, and latching wires LW, as illustrated inperspective in FIG. 6.

Referring now to FIG. 4, the basic meander line ML consists oftwenty-two copper lines arranged as illustrated. Each line may have awidth of 0.0 l 25 foot separated by 0.025 inch. The meander line ML isencapsulated in Tellite board Te, a low loss dielectric (polyolefin)having a dielectric constant of 2.38. The Tellite coating increases thepeak power hndling capability significantly.

The four rectangular ferrite toroids FT are slipped one by one over theend of the encapsulated meander line ML and along the meander line intothe positions indicated in FIG. 6. The relative positions indicated inFIG. 6 are preferred, but not essential. In the preferred arrangementindicated in FIG. 6, the first ferrite toroids to be encountered by thetransmit radar signal R enroute from the transmitter T to the dipoleelements E is the 192 delay core (8 bits), next the 24 delay core (Ibit), then the 48 delay core (2 bits), and finally the 96 delay core (4bits). Each ferrite toroid or core is separated from its neighbor by aspacer of insulating material I. These spacers I provide adequatemagnetic isolation between bits. The opposite ends of the meander lineML function as an external impedance-matching transformer as the radarsignal goes from Tellite to ferrite, and vice versa.

In the illustrative phase shifters being described, the l92 delay (8bits) has a width of 0.270 inch of ferrite, the 24 delay (I bit) has awidth of0.040 inch of ferrite, the 48 delay (2 bits) has a width of0.065 inch of ferrite, and the 96 delay (4 bits) has a width of 0. linch of ferrite. The total width (or length along the meander line) ofthe 4-unit or 4-bit phase shifter is 0.821 inch.

FIG. 5 is a cross-section view of the phase shifter. The encapsulatedmeander line ML goes through the center bore of the rectangular ferritetoroid FT. The toroid may have a height of 0.105 inch. A ground plane GPof aluminum or copper is placed on both the upper and lower sides of theferrite toroid and separated therefrom by Tellite insulation Te having athickness of 0.0195 inch.

CONTROL OF BINARY PHASE SHIFTERS Each set of 4-bit phase shiftersassociated with one radiating element can be controlled by a binarycounter. In the system of the present invention, each binary counterconsists of four stages of flip-flops in series. The number of inputpulses to each counter must be proportional to the position of thedipole element relative to the reference point. For an array with thedipole elements spaced equally apart and the reference point on onedipole, for example, the center dipole element EC, the input pulses toeach counter are proportional to the element number. This is illustratedin FIG. 3. By using a bit size determined by the equation A4 =2n/(2"l asproposed by the present invention, the least bit is 24, where n=4. Theproper ones complement is then available directly from the binarycounter, although the redundancy in the pulse numbers and 16 must beeliminated by circuitry, as previously indicated.

LOGIC As indicated above, each set of phase shifters associated with oneantenna element can be controlled by a binary counter. The countercontrolling the end dipole element furthest from the center of the arrayreceives all of the input pulses, and the phase shift of the end elementincreases directly with the number of input pulses. Ideally, the phaseshift in each of the other elements would then be proportional to theproduct of element position relative to the center of the array and thephase shift in the end element. This can be expressed as follows for al7-element array, where the end element is the eighth element from thecenter:

1) N/8 di N/8 P Ad) where N number of the element, counted from thecenter dJ phase-shift in the Nth element (by) phase-shift in the eighthelement P number of input pulses Adz least bit size It will be seen fromthe above that the phase shift in the Nth element is not necessarily aninteger multiple of the least bit size. Since only discrete incrementsin phase shift are available from the ferrite phase shifters, the phaseshift in the Nth element must be rounded off to the clostest integermultiple of the least bit size. The pulses which each counter mustreceive to give the proper round-off are listed in Table 1] below:

TABLE II Number of Input Pulses The ones" in a particular row of Tablell indicate the pulses which must be sent to the counter. For example,the counter controlling the third set of phase shifters must receive thesecond, fifth and seventh pulses. In some instances the value of thephase shift in the Nth element falls midway between two integermultiples of the least bit size. In these cases, the values shown inTable ll have been chosen so as to minimize the error in the beampointing angle. The numbers in Table I] repeat every eight pulses.

The end of the scan cycle may be detected by sensing a unique state of 5bits out of the total of 32 bits, comprised of 4 bits at each of 8ferrite phase shifters. A unique state exists, for example, when thecounter FF for dipole element No. 8 is 0100 and the element No. 1counter is 0! It).

In the system of the present invention, it is only necessary to providecounters to keep track of one half of the array. The other half of thearray is controlled by the complement. Stated another way, it is onlynecessary to calculate the phase-shift settings on one side of the arraysince the other side is the direct ones complement. The ones complementis available directly from the 4-bit binary counters FF each comprisedof four flipflops in series.

The proposed system permits the use of a single driver, if desired, forcorresponding bits on the two sides of the array.

What is claimed is:

l. A phased-array antenna system comprising:

a. an array of radiating elements;

b. a microwave signal source;

c. coupling means providing branch coupling between said signal sourceand the individual elements of said array;

d. phase shifters in the individual branches of said coupling means;

e. pulse-signal scan generating means for generating phase-shiftercontrol signals;

f. means coupling said scan generating means to individualphase-shifters in various branches to control the conditions of thephase shifters, thereby to control the phase shift of said microwavesignal in each branch as it passes therethrough to its associatedradiating element;

g. each of said phase shifters comprising a plurality of individualferrite units each of a different size to introduce a phase shiftcorresponding to one of a series of binary bits;

h. the ferrite unit which introduces a phase shift corresponding to theminimum bit being of a size to introduce a phase shift equal to 360divided by 2"l, where n is equal to the number of ferrite units in theferrite phase shifters.

2. A phased-array antenna system according to claim 1 characterized inthat the sum of the phase shifts capa ble of being introduced by theplurality of individual ferrite phase shifter units in each phaseshifter is equal to 360.

3. A phased-array antenna system according to claim 1 characterized inthat said phased-array antenna sys tern is characterized by having twocomplementary sides, each side comprising an even number of radiatingelements on each side of a center element; and further characterized inthat said coupling means is an assembly which is symmetrical on eachside of the branch to the center radiating element, and in that eachferrite phase shifter on one side of the center branch has acorresponding ferrite phase shifter on the other side of the centerbranch.

4. A phased-array antenna system according to claim 3 characterized inthat a pulse counter is provided for each phase shifter in each branchon one side only of the center branch.

5. A phased-array antenna system according to claim 4 characterized inthat said pulse counters comprise a plurality of bistable circuitsconnected in series.

6. A phased-array antenna system according to claim 3 characterized inthat driver means are provided for driving the ferrite phase shifters.

7. A phased-array antenna system according to claim 1 wherein n is equalto 4, and the phase shift introduced by the minimum ferrite units, whenin the one state, is equal to 24.

8. A phased-array antenna system according to claim I wherein n is equalto 4 and the phase shifts introduced by the four ferrite units when inthe one states are equal to 24, 48, 96 and 192.

9. A phased-array antenna system according to claim 6 characterized inthat said driver means includes common driver means for drivingcorresponding ferrite phase shifter units on the two sides of theantenna array.

10. A phased-array antenna system according to claim 6 characterized inthat the coupling means provides a corporate feed between the microwavesignal source and the individual elements of the array.

11. A phased-array antenna system according to claim 10 characterized:

a. in that each branch of the corporate feed includes a meander line,

b. in that the phase-shifter units are ferrite toroids through thealigned centers of which the meander line passes, and

c. in that each ferrite toroids unit of a phase shifter has a differentwidth along the meander line than the other toroid units of the samephase shifter.

12. A phased-array antenna system according to claim 11 characterized inthat the toroid having the greatest width and providing the largestphase shift is more remote from the radiating element than the othertoroids of the same phase shifter.

13. A phased-array antenna system according to claim 9 wherein:

a. said system includes means for establishing and controlling thedurations of a transmit period and a receive period;

b. said common driver means are adapted for setting the phase-shifterunits in one state for the trasmit period and in the opposite state forthe receive period;

c. the setting of the phase-shifter units on one side of the array isthe ones complement of the setting of the corresponding unit on theother side of the array during both of the transmit and receive periods.

14. A phased-array antenna system according to claim 13 wherein:

a. said driver means includes reset means;

b. said reset means are dual means including dual storage capacitors forcollecting energy to provide sufficient reset current to reset thephase-shifter units twice during each transmit-receive cycle.

15. A phased-array antenna system according to claim 14 characterized inthat a set driver is provided for each pair of corresponding ferritetoroids, and in that a separate dual reset or clear driver is providedfor each pair of corresponding 4-bit phase shifters.

16. A phased-array antenna system according to claim I wherein saidsystem has two complimentary sides, wherein said coupling means is anassembly which is symmetrical on each side of the branch to center, andwherein each ferrite phase shifter on one side of center has acorresponding ferrite phase shifter on the other side of center.

17. A phased-array antenna system according to claim 10 characterized inthat:

a. each branch of the corporate feed includes a meander line, and

b. the phase shifter units are ferrite toroids through the alignedcenters of which the meander line passes.

18. A phased-array antenna system according to.

claim 9 characterized in that each common driver means is utilized butonce during each transmit-receive cycle.

1. A phased-array antenna system comprising: a. an array of radiatingelements; b. a microwave signal source; c. coupling means providingbranch coupling between said signal source and the individual elementsof said array; d. phase shifters in the individual branches of saidcoupling means; e. pulse-signal scan generating means for generatingphaseshifter control signals; f. means coupling said scan generatingmeans to individual phase-shifters in various branches to control theconditions of the phase shifters, thereby to control the phase shift ofsaid microwave signal in each branch as it passes therethrough to itsassociated radiating element; g. each of said phase shifters comprisinga plurality of individual ferrite units each of a different size tointroduce a phase shift corresponding to one of a series of binary bits;h. the ferrite unit which introduces a phase shift corresponding to theminimum bit being of a size to introduce a phase shift equal to 360*divided by 2n-1, where n is equal to the number of ferrite units in theferrite phase shifters.
 2. A phased-array antenna system according toclaim 1 characterized in that the sum of the phase shifts capable ofbeing introduced by the plurality of individual ferrite phase shifterunits in each phase shifter is equal to 360*.
 3. A phased-array antennasystem according to claim 1 characterized in that said phased-arrayantenna system is characterized by having two complementary sides, eachside comprising an even number of radiating elements on each side of acenter element; and further characterized in that said coupling means isan assembly which is symmetrical on each side of the branch to thecenter radiating element, and in that each ferrite phase shifter on oneside of the center branch has a corresponding ferrite phase shifter onthe other side of the center branch.
 4. A phased-array antenna systemaccording to claim 3 characterized in that a pulse counter is providedfor each phase shifter in each branch on one side only of the centerbranch.
 5. A phased-array antenna system according to claim 4characterized in that said pulse counters comprise a plurality ofbistable circuits connected in series.
 6. A phased-array antenna systemaccording to claim 3 characterized in that driver means are provided fordriving the ferrite phase shifters.
 7. A phased-array antenna systemaccording to claim 1 wherein n is equal to 4, and the phase shiftintroduced by the minimum ferrite units, when in the one state, is equalto 24*.
 8. A phased-array antenna system according to claim 1 wherein nis equal to 4 and the phase shifts introduced by the four ferrite unitswhen in the one states are equal to 24*, 48*, 96* and 192*.
 9. Aphased-array antenna system according to claim 6 characterized in thatsaid driver means includes common driver means for driving correspondingferrite phase shifter units on the two sides of the antenna array.
 10. Aphased-array antenna system according to claim 6 characterized in thatthe coupling means provides a corporate feed between the microwavesignal source and the individual elements of the array.
 11. Aphased-array antenna system according to claim 10 characterized: a. inthat each branch of the corporate feed includes a meander line, b. inthat the phase-shifter units are ferrite toroids through the alignedcenters of which the meander line passes, and c. in that each ferritetoroids unit of a phase shifter has a different width along the meAnderline than the other toroid units of the same phase shifter.
 12. Aphased-array antenna system according to claim 11 characterized in thatthe toroid having the greatest width and providing the largest phaseshift is more remote from the radiating element than the other toroidsof the same phase shifter.
 13. A phased-array antenna system accordingto claim 9 wherein: a. said system includes means for establishing andcontrolling the durations of a transmit period and a receive period; b.said common driver means are adapted for setting the phase-shifter unitsin one state for the trasmit period and in the opposite state for thereceive period; c. the setting of the phase-shifter units on one side ofthe array is the one''s complement of the setting of the correspondingunit on the other side of the array during both of the transmit andreceive periods.
 14. A phased-array antenna system according to claim 13wherein: a. said driver means includes reset means; b. said reset meansare dual means including dual storage capacitors for collecting energyto provide sufficient reset current to reset the phase-shifter unitstwice during each transmit-receive cycle.
 15. A phased-array antennasystem according to claim 14 characterized in that a set driver isprovided for each pair of corresponding ferrite toroids, and in that aseparate dual reset or clear driver is provided for each pair ofcorresponding 4-bit phase shifters.
 16. A phased-array antenna systemaccording to claim 1 wherein said system has two complimentary sides,wherein said coupling means is an assembly which is symmetrical on eachside of the branch to center, and wherein each ferrite phase shifter onone side of center has a corresponding ferrite phase shifter on theother side of center.
 17. A phased-array antenna system according toclaim 10 characterized in that: a. each branch of the corporate feedincludes a meander line, and b. the phase shifter units are ferritetoroids through the aligned centers of which the meander line passes.18. A phased-array antenna system according to claim 9 characterized inthat each common driver means is utilized but once during eachtransmit-receive cycle.